i3 



to the function of the soredia. He believed them to be lateral 

 branches or buds (frofagines') and divided them into pulverulent 

 (fulverulentae), filamentous (scobiformes) and leaf-like {bracteo- 

 latae) . From this it is evident that his conception of soredia was 

 much more comprehensive than that of the present day, as this au- 

 thor, no doubt, included the so-called isidioid outgrowths as well as 

 the secondary thalloid branches. He stated that the J>ropag-/nes took 

 their origin from the surface of the thallus and had the power of de- 

 veloping into new lichens without any preliminary changes. Schreb- 

 er looked upon the soredia as gemmae rather than male reproduc- 

 tive organs, thus agreeing with Gartner within certain limitations. 

 Relhan 1 and others believed the apothecia were the female sexual 

 organs and the soredia the male sexual organs. One of the most 

 important works of the period was that of Hedwig. 2 He discovered 

 the spermagonia, and not only gave very good descriptions of these 

 organs, but of the apothecia, the spores and soredia as well. His 

 descriptions were greatly strengthened by good illustrations. His 

 conclusions were essentially as follows : The spermagonia which 

 are the male reproductive organs develop first ; subsequently the 

 apothecia and soredia are developed upon them. He believed the 

 apothecia with the spores to be the female reproductive organs, while 

 the soredia constituted the fertilizing elements or the true pollen. As 

 far as his conception of spermagonia and apothecia are concerned, 

 we see that Hedwig anticipated the opinions held by some lichenolo- 

 gists of to-day. His theory with regard to the function of the sore- 

 dia was, however, further from the truth than those of his predeces- 

 sors. 



We must also mention the rather unique experiments of De Can- 

 dolle 3 illustrating the method in which lichens were supposed to take 

 up their food-supply. This noted author employed a cochineal solu- 

 tion to observe the manner and rapidity with which various lichens 

 absorbed this substance. As the result, he grouped lichens as to the 

 manner in which he supposed them to absorb their food-supply, i. 

 Those which take their nourishment through the exterior. 2. Those 



'Relhan, R. Flora Cantabrigiensis. Cantabria. 1785. Supplement I. 1786. 

 Supplement II. 1788. 



2 Hedwig, J. Theoria Generationis et Fructificationis Plantarum Crvptogamarum 

 Linnaei. 1784. 



3 De Candolle, A. P. Premier essai sur la nutrition des Lichens. Journal de 

 Physique, de Chimie et d'Histoire naturelle, 47: 107. 179S. 



